1. Field of the Invention
This invention relates to an apparatus for variable-speed reproduction of audio and video data by scanning inclined recording tracks with a dynamic tracking head. It is applied for example to a digital video tape recorder utilizing a so-called D1 or D2 format in which digital audio data are dually recorded on the recording tracks.
2. Prior Art
With a so-called D1 or D2 format digital video tape recorder, digitized video and audio data are sequentially recorded on recording tracks T of the magnetic tape 10, which is inclined with respect to the longitudinal direction of the magnetic tape 10, as shown in FIG. 2, for example by a rotary magnetic head device RH as shown in FIG. 1.
The rotary magnetic head device RH shown in FIG. 1 is provided with two pairs of recording heads A.sub.1, B.sub.1 and A.sub.2, B.sub.2, arranged at an angular interval of 180.degree. with respect to each other, and two pairs of reproducing heads C.sub.1, D.sub.1 and C.sub.2, D.sub.2 arranged at an angular interval of 180.degree. with respect to each other. The two pairs of reproducing heads are arranged orthogonally to the recording heads A.sub.1, B.sub.1 and A.sub.2, B.sub.2 as shown in FIG. 1. Furthermore, the recording head pairs A.sub.1, B.sub.1 and A.sub.2, B.sub.2 and the reproducing head pairs C.sub.1, D.sub.1 and C.sub.2, D.sub.2 are arranged with a height difference corresponding to a width of one track. In the case of the NTSC system, for example, the rotary magnetic head device RH is driven at a rotational speed of 1.5 revolutions per field, thereby recording one-field video data on three sets of tracks T.sub.1 through T.sub.3 on the magnetic tape 10, as shown in FIG. 1.
Each inclined recording track on the magnetic tape 10 has a central portion as the video region in which video data V.sub.11, V.sub.12, V.sub.13, V.sub.21, V.sub.22, V.sub.23, . . ., for fields F.sub.1, F.sub.2, . . . , are recorded, and has inlet and outlet sides as the audio region in which time-base-compressed audio data A.sub.11, A.sub.12, A.sub.13, A.sub.21, A.sub.22, A.sub.23, . . . are recorded dually.
For variable-speed reproduction of a tape on which audio data, such as D1 or D2 format audio data, are recorded in a track direction on a block-by-block basis, there has been employed a processing system in which variable speed reproduction is performed with track jumps using a dynamic tracking head and wherein audio signal discontinuities produced by track jumps are compensated either by interpolation, muting, or a processing system in which the rotational speed of the drum and the tape sum ming speed are proportionally changed and all the audio and video tracks are reproduced in which, the audio signals are outputted directly and the video signals are subjected to thinning-out or supplementing operations.
However, the following problems arise when performing variable speed reproduction with a D1 or D2 formatting digital video tape recorder.
That is, with the former mentioned processing system employing a dynamic tracking head, noise may be produced at the junction points upon interpolation; and with the muting operation, voice dropout may be perceived with the latter system in which the drum speed and tape speed are proportionally changed, the reproducing frequency is changed due to changes in the rotational speed of the drum, so that the hardware load is increased as a result of time base processing of the video signals, while the voice pitch is changed. Moreover, to digitally output the voice, it is necessary to perform an operation to change the sampling frequency.